The Mohs scale of hardness was concieved of my German mineralogist, Friedrich Mohs, as a way of characterizing the scratch resistence of of minerals.
Diamond is the hardest known naturally occurring substance on earth with a hardness of 10. Rubies and Sapphires have a hardness of 9 and Topaz an 8. The Mohs scale is a ranking order, not a value. Diamonds are actually four times harder than Rubies and Sapphires. Rubies and Sapphires are twice as hard as Topaz.
|
Hardness
|
Gemstone
|
Dispersion
|
Refraction
|
|
10
|
Diamond
|
0.044
|
2.42
|
|
9
|
Ruby
|
0.018
|
1.77
|
|
|
Sapphire
|
0.018
|
1.77
|
|
|
Moissanite
|
0.104
|
2.65
|
|
8.5
|
Cubic Zirconia
|
0.058
|
2.17
|
|
|
Alexandrite
|
0.015
|
1.75
|
|
8
|
Topaz
|
0.014
|
1.61
|
|
7.5
|
Emerald
|
0.014
|
1.58
|
|
|
Aquamarine
|
0.014
|
1.56
|
|
7
|
Amethyst
|
0.013
|
1.54
|
|
6.5
|
Garnet
|
0.022
|
1.73
|
